Agricultural equipment, such as a tractor or a self-propelled combine-harvester, includes a prime mover which generates power to perform work. In the case of a tractor, for instance, the prime mover is often a diesel engine that generates power from a supply of diesel fuel. The diesel engine drives a transmission which moves wheels or treads to propel the tractor across a field. In addition to providing power to wheels through a transmission, tractors often include a power takeoff (PTO) which includes a shaft coupled to the transmission and driven by the engine.
The PTO can be coupled to a number of different types of equipment. Examples of such equipment include but are not limited to, log splitters, pumps, concrete mixers, mulchers, chippers, balers, harvesters, spreaders, and sprayers. Agricultural equipment also includes what is known as farm implements or attachments. In addition to the PTO, some tractors include a hydraulic machine having a hydraulic pump which can be used, for instance, to raise or lower a piece of equipment such as a mower.
In addition to agricultural vehicles, other work vehicles having prime movers include construction vehicles, forestry vehicles, lawn maintenance vehicles, as well as on-road vehicles such as those used to plow snow, spread salt, or vehicles with towing capability. While each of the work vehicles, including the agricultural equipment described above, often include combustion engines as the prime mover, some vehicles have electric motors, including stepper or DC motors, as prime movers. In addition, many work vehicles are configured to drive included apparatus such as hitch motion control.
The amount of power provided by the prime mover is limited by the power rating of the prime mover or by a control system which limits the amount of power which the prime mover provides, even though the prime mover may be capable of providing more power than that set by the control system. Some vehicle manufacturers, in fact, will use the same prime mover in a variety of different types of vehicles where the control system is configured to limit the prime mover's power output to different amounts depending on the functions being performed by the vehicle. For instance, while the prime mover may be capable of providing additional power, the operation of compatible accessories or equipment may suffer if too much power is provided to that equipment. Consequently, the power generated by the prime mover may not be limited by the actual power output of the prime mover, but instead may be limited by the control system to insure proper and long lived operation of the accessories or equipment.
While a vehicle's maximum power output is often limited by the control system, in some situations, the operator may desire to perform certain operations more quickly or with more power than what is allowed by the control system. Consequently, even though the prime mover can be capable of generating additional power, the additional power is unavailable. The operator, therefore, is not able to utilize all of the prime mover's power when needed, even if only needed for a short period of time. Consequently, what is needed therefore is a vehicle which can utilize all of a prime mover's power when desired by an operator.